High intensity X-ray sources are in increasing demand for applications such as for X-ray lithography for producing integrated circuits, computerized tomography for X-ray imaging, and for X-ray diffraction for analyzing materials. High intensity X-ray sources can be constructed by impinging a high intensity beam of electrons on an anode, but cooling the anode becomes a significant technical problem.
U.S. Pat. No. 1,160,177 to Kelley discloses an X-ray tube which uses an externally applied cooling medium with a fixed anode.
Some improvement in distributing the heat from the beam can be achieved by steering the electron beam to different parts of the anode. U.S. Pat. Nos. 2,229,152 to Walsweer and 4,336,476 to Holland disclose an anode sealed entirely in the vacuum which rotates in response to the field from coils exterior to the vacuum. The heat from the anode must be conducted through bearings or radiated through the vacuum to an external cap.
U.S. Pat. No. 4,128,781 to Flisikowski et al discloses an X-ray tube having a cathode rotatable relative to an anode. Electrons from a rotating cathode are incident on a stationary anode ring. The X-rays are emitted from different positions in space as the cathode is rotated. For many applications, it is important that the X-rays be emitted from a position fixed in space.